Dataset Information

Prospects for Engineering Biophysical CO₂ Concentrating Mechanisms into Land Plants to Enhance Yields.

ABSTRACT: Although cyanobacteria and algae represent a small fraction of the biomass of all primary producers, their photosynthetic activity accounts for roughly half of the daily CO₂ fixation that occurs on Earth. These microorganisms are able to accomplish this feat by enhancing the activity of the CO₂-fixing enzyme Rubisco using biophysical CO₂ concentrating mechanisms (CCMs). Biophysical CCMs operate by concentrating bicarbonate and converting it into CO₂ in a compartment that houses Rubisco (in contrast with other CCMs that concentrate CO₂ via an organic intermediate, such as malate in the case of C₄ CCMs). This activity provides Rubisco with a high concentration of its substrate, thereby increasing its reaction rate. The genetic engineering of a biophysical CCM into land plants is being pursued as a strategy to increase crop yields. This review focuses on the progress toward understanding the molecular components of cyanobacterial and algal CCMs, as well as recent advances toward engineering these components into land plants.

SUBMITTER: Hennacy JH

PROVIDER: S-EPMC7845915 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Prospects for Engineering Biophysical CO2 Concentrating Mechanisms into Land Plants to Enhance Yields.

Hennacy Jessica H JH Jonikas Martin C MC

Annual review of plant biology 20200309

Although cyanobacteria and algae represent a small fraction of the biomass of all primary producers, their photosynthetic activity accounts for roughly half of the daily CO2 fixation that occurs on Earth. These microorganisms are able to accomplish this feat by enhancing the activity of the CO2-fixing enzyme Rubisco using biophysical CO2 concentrating mechanisms (CCMs). Biophysical CCMs operate by concentrating bicarbonate and converting it into CO2 in ...[more]

PMID: 32151155

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Project description:Ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (RuBisCO) is the carbon-fixing enzyme present in most photosynthetic organisms, converting CO2 into organic matter. Globally, photosynthetic efficiency in terrestrial plants has become increasingly challenged in recent decades due to a rapid increase in atmospheric CO2 and associated changes toward warmer and dryer environments. Well adapted for these new climatic conditions, the C4 photosynthetic pathway utilizes carbon concentrating mechanisms to increase CO2 concentrations surrounding RuBisCO, suppressing photorespiration from the oxygenase catalyzed reaction with O2. The energy efficiency of C3 photosynthesis, from which the C4 pathway evolved, is thought to rely critically on an uninterrupted supply of chloroplast CO2. Part of the homeostatic mechanism that maintains this constancy of supply involves the CO2 produced as a byproduct of photorespiration in a negative feedback loop. Analyzing the database of RuBisCO kinetic parameters, we suggest that in genera (Flaveria and Panicum) for which both C3 and C4 examples are available, the C4 pathway evolved only from C3 ancestors possessing much lower than the average carboxylase specificity relative to that of the oxygenase reaction (S C/O=S C/S O), and hence, the higher CO2 levels required for development of the photorespiratory CO2 pump (C2 photosynthesis) essential in the initial stages of C4 evolution, while in the later stage (final optimization phase in the Flaveria model) increased CO2 turnover may have occurred, which would have been supported by the higher CO2 levels. Otherwise, C4 RuBisCO kinetic traits remain little changed from the ancestral C3 species. At the opposite end of the spectrum, C3 plants (from Limonium) with higher than average S C/O, which may be associated with the ability of increased CO2, relative to O2, affinity to offset reduced photorespiration and chloroplast CO2 levels, can tolerate high stress environments. It is suggested that, instead of inherently constrained by its kinetic mechanism, RuBisCO possesses the extensive kinetic plasticity necessary for adaptation to changes in photorespiration that occur in the homeostatic regulation of CO2 supply under a broad range of abiotic environmental conditions.

Dataset Information

Prospects for Engineering Biophysical CO₂ Concentrating Mechanisms into Land Plants to Enhance Yields.

Publications

Prospects for Engineering Biophysical CO<sub>2</sub> Concentrating Mechanisms into Land Plants to Enhance Yields.

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